Surface plasmon resonances involve collective oscillations of electrons at a boundary of a conductive metal film, or of an array of conductive metal particles, that are stimulated by the electromagnetic waves of incident light. For resonance to occur, the excitation light frequency must be near the frequency of the collective coherent oscillations of the free electrons or surface plasmon frequency. Since the surface plasmon electron oscillation frequency depends on dielectric constants of the metal film at the surface, and of medium adjacent to the metal film at the surface, changes in those dielectric constants may alter resonances.
P. Debackere, et al., A Biosensor based on Surface Plasmon Interference, Proceedings Symposium IEEE/LEOS Benelux Chapter, 2006, Eindhoven, pg. 69-72, describes biosensors where a surface plasmon resonance is excited and read with infrared light, the resonance measurably changing with changes in dielectric constant at a surface of the sensor due to presence or absence of analytes in adjacent media. Debackere, et al., does not describe use of conductive-particle arrays, or of surface plasmon resonances in such arrays.
Kravets V. V., Yeshchenko O. A., Gozhenko V. V., Ocola L. E., Smith D., Vedral J. V., and Pinchuk A. O., Electrodynamic coupling in regular arrays of gold nanocylinders, (2012) Journal of Physics D: Applied Physics 45 (2012) 045102, describes a method of creating arrays of gold nanocylinders having particle sizes between 50 and 200 nanometers and which exhibit surface plasmon resonances.